Electron beam heating systems have been commonly used for vacuum furnace metal refining and also for vaporizing material to be deposited in high vacuum deposition processes. In such systems, one or more electron beam gun assemblies direct high energy electron beams onto the target to be heated, generally by means of magnetic fields that extend transversely of a beam of electrons so as to deflect the beam 180.degree. or more into a curving path and onto the target. In beam deflection of such degree, the electron beam source can be positioned beyond a line-of-sight from the target so that it is protected from contamination by vaporized target metal. The development of electron beam heating systems of this type has over a number of years resulted in numerous improvements, such as various magnetic devices for controlling the size and location of the spot at which the electron beam impacts the target. In general, such prior art devices use transverse magnetic fields to cause angular deflection of the electron beam 180.degree. or more along a path of continuous positive curvature that extends from the source itself to the target, an example being shown in U.S. Pat. No. 3,450,824, granted June 17, 1969 to Hanks et al.
The present invention concerns a further improvement for increasing the functional efficiency of the electron beam wherein the beam is controlled so as to have a unique path that is found to provide more efficient heating of the target.